Ocean Noise Pollution
In the marine environment, acoustics is of paramount importance. However, the world’s oceans are getting louder and louder and the ocean noise pollution severely impacts marine life. In certain marine areas, the ocean noise level has doubled every ten years over the last sixty years.
The increased ship traffic generates a heightened dense acoustic fog that distorts the perception instincts of marine life. The meter-high propellers of the giant freighters create a deafening noise underwater. Collisions between large ships and whales are usually fatal for the animals. Also the noise from oil platforms and the air pressure cannons for oil exploration generate enormous noise, which pollutes an area of up to 250’000 square kilometers (96’500 square miles). Invertebrates suffer internal bleeding as a result, which can lead to death.
The most noticeable consequence of ocean noise pollution is the stranding of whales and other marine mammals. Strandings have been observed to be particularly frequent after naval sonar maneuver. These sonar systems for the location of submarines can be as loud as a rocket launch (up to 260 decibels) and can be heard underwater within a radius of 3’000 kilometers (1’860 miles). Extreme sound events like these inflict vascular damage in the brain, lungs and other organs. It can also be the case that animals panic and surface far too fast. Thereby nitrogen bubbles in the blood lead to cases of the bends and potentially deadly embolism.
As is the case for humans, where the absolute pain limit is 120 decibels, marine animals are also susceptible to hearing damage as a result of extremely loud sounds. For many marine creatures, their hearing is a vital way to communicate, navigate, hunt prey, sense danger and find a partner. Hearing damage is not the only physical mark that ocean noise pollution can leave though. The shoaling structure of fish can be sent into chaos, impaired growth has been observed in shrimp and even cell changes have been detected in lobsters.
Ocean noise pollution leads to marine animals fleeing their habitats, never to return. Some are directly induced to flee while others are compelled to as their prey have left. Ocean noise pollution has a disruptive impact in mating and suckling the young with some serious consequences in cases when species are already under threat for other reasons.
Ocean noise has a negative effect on at least 55 marine species. A 10% reduction in the speed of the transport ships would already reduce the noise pollution under water by 40%. In addition, CO2 emissions and the risk of collisions with whales would be significantly reduced. Yet, binding rules and limitations for noise-generating technologies at sea are still missing.